The present invention relates generally to the generation of eye and bit error rate diagrams and more particularly to producing a two-dimensional probability density function (PDF) eye diagram and a Bit Error Rate eye arrays for display on a display device.
Digital sampling oscilloscopes acquire waveform records of data patterns under test to generate and display eye diagrams representing unit intervals of the data pattern. The digital sampling oscilloscope has sampling circuitry that acquires very accurate data samples of the data pattern under test. However, the eye diagrams are approximations of the probability of any particular data sample being at a particular location due to the limited number of samples acquired by the sampling oscilloscope. These approximation places limitations on the accuracy of the measurement analysis of the eye diagram. The generation of a Bit Error Rate eye from eye diagram data has limited accuracy. To increase the accuracy of the eye diagram and the resulting measurement analysis requires the acquisition of large quantities of data samples of the data pattern under test. Such acquisitions would take days and months of continuous acquisitions.
A Bit Error Rate Tester (BERT) is another type of measurement instrument that acquires data samples of a data pattern under test. The BERT has specialized circuitry that can acquire extremely large records (giga-samples of data) over a relatively short period of time to generate eye diagrams and Bit Error Rate eyes. However, there are tradeoffs between the extremely fast acquisition of data samples and data sample accuracy. The acquisition circuits in the BERT have inferior flatness and frequency response resulting in acquired data samples having inaccurate amplitude levels. These inaccuracies are translated into eye diagrams and Bit Error Rate eyes. The resulting measurement analysis of the eye diagram and Bit Error Rate eye will have these inaccuracies.
What is needed is a method of producing highly accurate two-dimensional probability (PDF) eye diagram and Bit Error Rate eye arrays from a limited number of samples from an oscilloscope or other type of digitizing instrument. The method should accurately represent the data pattern under test and the vertical and horizontal uncertainties (i.e. noise and jitter) in the data pattern. The vertical and horizontal uncertainties should be a statistically accurate representation of these uncertainties. The statistically accurate vertical and horizontal uncertainties should be combinable with the accurate representation of the data pattern under test to produce the accurate two-dimensional probability (PDF) eye diagram and Bit Error Rate eye arrays for displaying as a PDF eye diagram and Bit Error Rate eye.